1. Field of the Invention
The present invention relates to a ring gear that transmits starting torque output from a starter motor to a crankshaft side member, which rotates with a crankshaft of an internal combustion engine, through a one-way clutch, an internal combustion engine-starting torque-transmission mechanism using the ring gear, and relates to a method of manufacturing the ring gear.
2. Description of the Related Art
In order to start an internal combustion engine, an internal combustion engine-starting torque-transmission mechanism that cranks the engine using torque from a starter motor via gear mesh between a pinion and a ring gear is used. As the internal combustion engine-starting torque-transmission mechanism, a mechanism is already available in which a one-way clutch is disposed on a path through which starting torque is transmitted from a ring gear to a crankshaft (see Japanese Patent Application Publication No. 10-122107 (JP-A-10-122107) (page 3, FIG. 1), and Japanese Patent Application Publication No. 63-18185 (JP-A-63-18185) (page 2, FIG. 2), for example). With this configuration, it is possible to transmit torque from the starter motor to the internal combustion engine when the internal combustion engine is started, and it is possible to stop rotation of the starter motor after engine start is completed, with the mesh between the pinion and the ring gear maintained. That is, it is possible to construct an internal combustion engine-starting torque-transmission mechanism of constant-mesh type.
In such an internal combustion engine-starting torque-transmission mechanism using a one-way clutch, it is necessary to form one race portion of the one-way clutch, with which sprags or the like are engaged, in a ring gear, and to finish the surface of the race with high precision. In addition, in order to provide sealing against lubricating oil supplied to the one-way clutch, it is necessary to form a disposition surface on which a seal ring is disposed, or a contact surface with which a seal ring is in contact, and to finish the disposition surface or the contact surface with high precision.
However, it becomes necessary to change the size and the shape of the ring gear depending on the type of internal combustion engine, and, in some cases, using the same processing apparatuses and processing procedures may cause insufficiency in precision. Accordingly, in order to constantly carry out processing of the ring gear with high precision independently of the type of internal combustion engine, relatively significant changes in the processing apparatuses and processing procedures have to be made depending on the type of internal combustion engine, which causes a problem of an increase in manufacturing cost.